1. Field of the Invention
The present invention relates to a pilfer-proof cap made of synthetic resins to be put on a mouth portion of containers such as bottles for use in drinks.
2. Description of the Prior Art
A pilfer-proof cap having a container-sealing packing (hereinafter referred to as a packing), in which said packing is held at an appointed position on an inside surface of a top wall of a cap to be simultaneously lifted up together with said cap, whereby releasing a sealing for said container by the packing, when said cap is removed from said container, has been proposed (refer to Japanese Publication No. Sho 62-18421).
However, with such a construction, there has still been the possibility that the packing is lifted up together with the cap or is not removed from, but rather is rotated together with the cap to release said sealing for the container, whereby breaking an airtightness, while a bridge holding a band for mechanically engaging the cap with said mouth portion of the container is not broken, when a cap-opening action out of mischief and the like, so-called a slight rotation, is conducted while the cap is not fully removed.
The cap of this type is not preferably used in view of a protection for contents in the container in the case where a pressure within a tightly sealed-up container filled with contents is higher than that outside of said container (1), the case where said pressure within the tightly sealed-up container becomes equal to a pressure outside of the container and a packing is continuously adhered closely to a mouth portion of the container (2), or the case where it is used for tightly sealing up the container filled with a liquid heat treated at a high temperature or the container which is subjected to a high-temperature heat treatment after being filled with a liquid followed by being cooled to room temperature and, as a result, an inner pressure of the tightly sealed-up container is reduced and a packing is continuously adhered closely to a mouth portion of the container by a vacuum generated within the container (3). For example, in the case of the above described (1), a gas is leaked, and in cases of the above described (2), (3), the open air is apt to enter the container together with bacteria and, consequently, the contents of the container are apt to be denatured and corrupted in all of the above described cases (1), (2) and (3).